Numerous fatal human diseases originate with the formation and progressive growth of deposits or “plaques” in tissues or organs. The materials for such plaques are generally organic or inorganic molecules that derive from the fluid bathing a particular organ. Progressive plaque build-up can occur in areas throughout the body, but organs particularly at risk are the heart, brain, kidney, gall bladder and vasculature.
Plaque development can be a gradual process, occurring over the course of years, or even decades. Likewise, the pathogenic consequences of such plaques can take a long time to appear. For example, atherosclerotic processes in blood vessels may begin in early childhood, continue without evident symptoms through middle age (Viles-Gonzalez J F et al, 2004), before developing into a potentially life-threatening cardiovascular condition later in the individual's life.
The American Heart Association classifies atherosclerotic processes based on the components of the plaques. The more fibrous stable preatheroma plaques (type I to III) have relatively lower extra cellular lipid content. In contrast atheromatic plaques (type IV and Va) typically contain higher levels of extra-cellular lipids, cholesterol, calcium crystals and thin fibrous caps, making them less stable and vulnerable to rupture (Serfaty J M et al, 2001). When unstable plaques rupture, they can generate thromboses accompanied by serious life-threatening conditions such as Myocardial Infarction, stroke and thromboembolic events (Rauch U et al, 2001).
Plaques also accumulate in other diseases including but not limited to Alzheimer's-disease, Parkinson's disease, and other amyloid protein aggregation diseases. These diseases are characterized by abnormal depositions of misfolded proteins in tissues and organs. These depositions often begin with the formation of insoluble aggregates consisting of amyloid proteins and/or peptides alone or in combination with certain metallic elements. Over the course of years, or even decades, amyloid aggregations can become pathogenic plaques; but the process of plaque development is not clearly understood. A better understanding of the assembly of amyloid plaque complexes and of the degree of their pathogenicity would enable the development of highly-targeted therapies.
Deposition of amyloid aggregates occurs on the walls of arteries, arterioles, cerebral vasculature, capillaries and veins of the cerebrovascular system of AD patients and normal aged individuals (Burgermeister et al, 2000; Walker L C et al, 1999). Epidemiological, pathological and clinical studies provide evidence that vascular factors may play a significant role in the pathogenesis of neurological diseases and particularly in the case of AD (de la Torre J C 2004; 2005). This hypothesis is reinforced by multiple studies carried out in transgenic animal models that relate over-expression of amyloid precursor protein (APP) to neuropathological conditions observed alike in the AD patients (Miao J et al, 2005). In addition, progressive accumulation of amyloid plaques on the sides of carotid and cerebral arteries could impair normal blood flow in the cerebrovascular system, eventually leading to the development of dementia and cerebral amyloid angiopathy (CAA) (Kimchi E Y et al, 2001; Beckmann N et al, 2003). Neuroinflammation is another related pathogenic event occurring in the cerebral vascular region of transgenic mice expressing human abeta42 peptides (Miao J et al, 2005).
Other methods for screening effective drugs for the treatment of Alzheimer's disease exist. One method, described in U.S. Pat. No. 6,214,569, concerns the screening of inhibitors of the formation of Alzheimer β-peptide filaments. The formation of such filaments in said invention involves incubating the Aβ peptide at room temperature, enabling the spontaneous formation of amyloid filaments.
Another method of screening for effective drugs for Alzheimer's disease is described in U.S. Pat. No. 6,218,506 B1. In this invention, amyloid β peptides first assemble into non-fibrillar structures after suspension in anhydrous DMSO and then, in certain embodiments, the assembled fibrils are used in animal studies, such as to evaluate the long-term potentiation response in animals.
A method for identifying and characterizing inhibitors of protein filament formation, including the formation of tau filaments in Alzheimer's patients and α-synuclein filaments in Parkinson's patients is described in U.S. Pat. No. 7,172,875 B2. In this invention, protein monomers are combined under physiological conditions with a fibrillization inducer in the presence or absence of a test agent.
A method of treating Alzheimer's Disease is described in U.S. Pat. No. 7,179,463 B2. In this invention a subject having or suspected of having Alzheimer's Disease is administered an antibody that had been raised against a protofibril containing Aβ-Arc peptide.
A method of isolating and assembling misfolded or partially misfolded proteins in blood and other biological materials is described in U.S. Pat. No. 7,138,255 B2. In some embodiments of this invention, “proteons” comprised of misfolded proteins present in the blood assemble on proteon nucleation centers.
However, drug discovery in this area is currently hindered by the absence of a biochemical model system that mimic the mature or late stage forms of amyloid plaque in vitro in a relatively short period of time. Accordingly, there is a great need to develop in vitro processes to synthesize physiologically relevant amyloid and amyloid-like plaque formations for testing and drug discovery purposes.